1. Field of the Invention
The present invention relates to a power semiconductor device and a manufacturing method thereof, and more particularly, to a power semiconductor device having low gate input resistance and a manufacturing method thereof.
2. Description of the Prior Art
In the trench transistor, a gate electrode is disposed in a trench of a substrate, and a source electrode and a drain electrode are respectively disposed at an upper side and a lower side of the gate electrode. A channel is vertically formed between the source electrode and the drain electrode. Accordingly, some advantages are provided by this structure, such as a high voltage-withstand ability, low on-resistance, and a large current. As a result, the trench transistors are widely applied in power management, such as switching power supplies, integrated circuits used in power management, backlight power supplies, and motor controllers.
Generally, the trench transistor is operated with a large current. In order to reduce the power loss, a gate metal bus line is disposed to provide an additional input path of a gate voltage for improving the gate input resistance. Please refer to FIG. 1, which schematically illustrates a layout of a power semiconductor device in the prior art. To simplify the description, only some elements are shown in FIG. 1. As shown in FIG. 1, two segments of the source metal layer 11 and one gate metal layer 12 are disposed on a substrate 10, and trench transistors (not shown in the figure) are disposed under each of the source metal layers 11. The source metal layer 11 is configured to provide a source voltage to a source electrode of the trench transistor, and the gate metal layer 12 is configured to provide a gate voltage to a gate electrode of the trench transistor. Furthermore, the gate metal layer 12 has a gate metal bus line 13 for decreasing the gate input resistance.
However, in order to reduce the gate input resistance, an additional area is required for disposing the gate metal bus line 13 in the power semiconductor device of the prior art. Accordingly, the gate metal bus line 13 divides the source metal layer 11 into two segments, and the gate metal bus line 13 can transmit the gate voltage to the gate electrodes of the trench transistors under each of the source metal layers 11. Therefore, the area of each segment of the source metal layer 11 is reduced, and it increases manufacturing costs and difficulty in the subsequent bonding and packaging processes. Moreover, an additional space is required to isolate the gate metal bus line 13 and the source metal layer 11, and it further reduces the bonding area and decreases the integration degree. As a result, an improvement of the power semiconductor device in the prior art is necessary to reduce the gate input resistance and to keep the entire source metal layer 11 complete.